The present invention relates to a method for manufacturing a liquid crystal display (referred to as LCD hereinafter), and more particularly to an LCD manufacturing method capable of obtaining an LCD having high display grade and high reliability.
An orientation film for performing alignment control of liquid crystal material in the LCD is formed so as to cover not only a display area on an electrode substrate but also a seal-forming area outside the display area. However, the orientation film is not formed on external connection terminals in order to connect with connecting terminals of peripheral parts which constitutes part of the LCD.
When a surface of the orientation film on the electrode substrate is processed by a rubbing method, the external connection terminals are directly subject to friction by a rubbing cloth. This leads to a problem that the external connection terminals are prone to becoming damaged and dirtied by foreign matters and thereby conduction failures might occur when electrically connected to the connecting terminals of the peripheral parts. Further, there is a difference in level between one region where the orientation film is formed and the other region where the orientation film is not formed. Therefore, the difference in level allows pile (fine threads) of the rubbing cloth to be disordered at the time of rubbing. This leads to another problem, non-uniformity on the orientation film that appears in the display area and deteriorates the display grade when the disorder of the pile is transferred to the orientation film.
As measures for solving these problems, there has been proposed a method, as disclosed in Japanese Patent Laid-open Publication Nos. HEI 5-11250 and HEI 7-301776, in which after forming an orientation film as a protective film on the external connection terminals and then performing the orientation process to the surface of the orientation film by the rubbing method, the orientation film is removed by plasma etching so that the external connection terminals are electrically connected to terminals of peripheral parts.
However, since the orientation film is removed by plasma etching, the equipment for plasma etching is large in scale. Also disadvantages in processing capacity and equipment investment are incurred and a problem of high cost arises.
Meanwhile, there has recently been proposed a method for removing the orientation film in which molecular bonds of the orientation film are decomposed and sublimated by using a mercury ultraviolet lamp. With reference to FIG. 3, numeral 20 denotes an ultraviolet beam 20 from a mercury ultraviolet lamp and numeral 21 denotes an electrode substrate. Numerals 22a and 22b denote a display electrode and external connection terminals continuous from the display electrode, respectively. The display electrode 22a and the external connection terminals 22b are formed from a transparent electrically conducting film. Numerals 23 and 24 denote a transparent insulating film and an orientation film, respectively. Also, numeral 25 denotes a mask which has openings so as to be open above regions of the orientation film 24 overlying the external connection terminals 22b. After the mask 25 is placed above the electrode substrate 21, the orientation film 24 on the external connection terminals 22b is irradiated via the mask 25 with the ultraviolet beam 20 from the mercury ultraviolet lamp. Thereby the orientation film 24 on the external connection terminals 22b is removed.
However, in the above method for removing the orientation film 24, it is impossible to accurately control the irradiation range of the ultraviolet beam 20 from the mercury ultraviolet lamp. This is because the ultraviolet beam 20 does not have sufficient directivity. Accordingly, the mask 25 should be used and there arises a problem that production efficiency of the LCD is lowered since it is necessary to add a process of placing the mask 25.
Also, it is difficult to concentrate light intensities of the mercury ultraviolet lamp to the wavelength range in which molecular bonds of the orientation film 24 are decomposed and sublimated. As a result, the electrodes 22a of the transparent conducting film, the insulating film 23, a color filter and other members located near the orientation film 24 that is to be removed are adversely affected, involving faulty phenomena such as deformation due to temperature increases, deterioration of strength, deterioration of coloring and transparency caused by photochemical changes.